Spark plug and method of making the same



Oct. 8, 1929. w. B.- SMITS SPARK PLUG AND METHOD OF IAKING THE SAMEFiled Nov. 22, 1927 E M GA J man rm er firm/vii assed .8, 1929 I uN-rrsosrA-Tss PATENTOFFICE 'WIJTZE am mus, OI MEL-WHORE, Gm!

PLUG AND METHOD 01' mo TEE ELIE Application and nu ber 22-,- 1927,Serial in. 235,000, and in Germany 1mm in, ms.

This invention relates to the production of spark plugs, and has for itsobject to improve the quality of such plugs as regards their efficiencyand durability. This 0 ject is obtained by filling the space between.the insulator and the body of the plug by a material in powdered orpulverized form, this material having the ualities of tightening and ofconducting the heat, further of equalizing the difierent degrees ofexpansion of the insulator and the body of the plug respectively and ofifastening the insulator in the plug. This eliminates the disadvantagesmet hitherto in spark plugs of usual con struction which are subject tofrequent cracking of the insulator and to rapid wear.

One embodiment of the spark plug is shown by Way of example in theaccompanying drawing, in which Fig. 1, is a sectional view ofa plugshowing the way of applying the method of the inventiong Fig. 2 shows apart of the plug represented in Fig. 1 after the method of the inventionhas come to an end.

In the embodiment shown in the drawing, 1 represents the usual metallicbody roduced by a casting process or otherwise) flaving a threaded part2 to be inserted into the cylinder head. 3 indicates an insulator madeof porcelain or another material havin similar insulating qualities. Oneelectrode or sparking pin is represented by 4, Whereas the otherelectrode is secured to part 2 of the plug. A nut 6 serves for holdingthe electrical wire. Between the inside surface of part 1 and theoutside surface of insulator 3 a space 7-is left. A ring 8 of a softmetal which is able to resist the working temperatures is insertedbefore the insulator 3 is inserted. The ring 8 rests upon a shoulderformed in part land is pressed against it by edge 9 of the insulator 3.The space 7 is thereby tightly closed against the inner space ofthreaded portion 2.

Space 7 is filled after insertion of insulator 3 by apulveriz'd'material 10 having tightening and heaticonducting qualities,this material preferably consisting of pulverized -x means of a'suitabletool 11 this material is ressed rather stron 1 into the space 7, so t atthis ma be filled liy a dense mass. This mass touc ess all parts of theouter surface of insulator 3 as well as of the inner surface of plug 1and fills the space 7 in such a manner that irregularities of theformation of said surface which may em'st are equalized so thateverywhere a good heat conductivity and a tight fit is obtained. Filledspace '5 may be made tight to the out side by providing a rim 12 or thelike which is bent over the manner shown in 2 for closing purposes. Aloose metallic ring may, however, be used instead of l2.

The dificulty to be overcome in the art of making spark plugs resideschiefly in the difference of rates of expansion due to influence betweenthe insulator and the metallic body. The thermal rate of expansion ofthe insulator bein much lower than that of the metallic plugiody it is anecessity to carry away the heat from the insulator as quickly aspossible which heat would otherwise be stored in it ,and would give riseto craekings. It, therefore, is a known fact that the layer 10 providedin space 7 between insulator and body must be of high heat conductivity.This layer must further be of such quality that for allforthcomingtemperatures it fills out space 7 in g such a manner thatinsulator 3 is fastened and held tight under all circumstances so thatno gas may escape from the cylinder. These conditions may not fully becomplied with by existing constructions of spark plugs. They arehowever, complied with by a spark plug made in accordance with theinvention.-

By taking a wdered or pulverized ma terial, referabFy a metal or amixture of metals or filling out space 7, it becomes possible to choosesuch material as regards its rate of expansion in such a manner that thelayer 10 in space 7 is, so to speak, able to equalize the differentrates of expansion of the insulator and of the metallicbodyrespectively. The layer 10 (if made of pulverized material havingthe right rate of expansion) is expanded by the heat of the working temperatures in such a manner as to fully fill out the space (which wouldbe greater for a Lore :21 a

higher tempereeures for lower ones} wiiclsout danger of insiim zor inits sesfizeor of rise to s This is due to fine srueture or? finepuiverizedmesud may not he stsined by methods known hitherto. T nepuiverized state of L ne materiel i brought into space '2' further lies"one result that all mequfiaies ere equels osrir line 1.; is ibe lirenee such esee'rness M Ur. eis surface F's en e eireuisr sue, p

cause The meterisi 2-8 pre- . erred by s iooi Ti in. is inrtlier of usethe i in es dry 2, state so that the insulator (were; mu semis-i o'fhygroscopic rnsierisl) not T is necessa y to provide means for eiosisgthe space 7 the isner spaee of portion 2 shat is against the cyiinder.is done in the drawing oy ring 8 which is pressed tightly against itsseat loy' siae insulator 3.

' it further is advantageous to use other means such as rim 12 shown inthe drawing for closing space 7 against the outside.

Aluminium, copper or another metal or alloy may be used es the materiel10 or as part of it.

Having described my invention, what I claim as new and desire to secureby Letters Patent of the United States is:

- good conductor of 1. In a spark plug having a hollow metal body and aninsulatlng body disposed illegain, a pulverized metal-containing packingbetween said metal body and said insulating bodies, said packing beinga, good conductor of heat and having a, coeficieni: of expansions'dapted to vary its volume directly as the volume of the space itoccupies varies with the operating temperature range.

2. A. spark plug having an insulating body disposed within a hollowmetal loody, and a layer of pulverized metal-containing material betweensaid metal body and said insulsfiing body, said pulverized layer being aBestsndheving a co efioient of expansion capable oi equalizing raisesthe difiereno rates of expansion of the insider.- ing body end of thehoiiow motel body.

3. spark plug comprising a, hollow metal liody herring on enlargedtapered; opening at one end, o shoulder at the end of said taperedopening, e soft metallic ring on said shoulder, e tapered insulstingbody disposed in she sforesuid opening and resting on the metallic ring,and a, pulverized layer of metal-conraining materiel separating thesides of the insulating body end the enlarged opening, said pulverizedlayer being a good conductor of best and hevin e coeficient of expansionoepuble of equalizing the rates of expansion of the insulating body andof the hollow bodyso as to always i l the space between rue aforesaidbodies.

